The Persistence of Herbicide Residues in Fadama and Upland Soils in Plateau State, Nigeria

Abstract

Fadama and upland soil in Plateau State, Nigeria were monitored for the residues of five herbicides widely used for farming within the areas under investigation from June 2010 to June 2012. The average concentration in mg/kg of the residues in the soils were; atrazine (0.123), 2,4-D (0.013), paraquat (0.020), oxadiazon (0.100) and pendimethalin (0.020) for fadama soils. While the concentration of the atrazine, 2,4-D, paraquat, oxadiazon and pendimethalin in upland soils were 0.180, 0.023, 0.030, 0.0130 and 0.010 mg/kg respectively, suggesting the herbicide residues persist at considerably high concentration. Physicochemical factors such as pH, Low Organic matter and textural characteristics of the soils were the factors identified to contribute to the persistence of the herbicides. Other factors like microbial activities were also suggested to play significant roles in the degradation or the persistence of the herbicide residues. The distributions of the residues were monitored seasonally over a period of time within the study area. This was sampled for laboratory analysis during the farming seasons covering planting to harvesting time where most of these herbicides and other chemical farm inputs are still believed to be active in the soils within the study area. The herbicides under investigation were observed to persist more in fadama soils which is characterized by high water holding capacity and low organic matter content.   Keywords: Persistence, herbicide residues, fadama, upland, soil